DESCRIPTION: The processes of axonal transport are essential for neuronal function and underlie neuronal growth, maintenance and regeneration. Understanding axonal transport is a key to understanding the dynamics of the nervous system. Functions as diverse as conduction of the action potential, release of neurotransmitter, generation and maintenance of the presynaptic terminal, neuronal development and regeneration, and maintenance of neuronal architecture depend critically on fast axonal transport of membrane bounded organelles along microtubules. Similarly, a wide range of neuropathological conditions, including diabetic and toxic neuropathies, motor neuron diseases and degenerative diseases of the nervous system have characteristics expected from a disruption of fast axonal transport. Based on studies of fast axonal transport in isolated axoplasm from the squid giant axon, a new family of mechanochemical ATPases, the kinesins, has been defined. Kinesins are motors for the movement of membrane bounded organelles in the anterograde direction of fast axonal transport. Previous work by the applicant has answered a number of questions about the biochemistry, molecular biology, cell biology, and neurobiology of kinesin. The applicant proposes that different kinesin transcripts and subunits in the neuron reflect distinct physiological roles. The proposed experiments constitute a multidisciplinary effort that will use methods from both cellular and molecular biology to define the functional architecture of neuronal kinesins. These experiments will provide a molecular basis for kinesin isoforms and test hypotheses about their physiological roles. Kinesin is subject to posttranslational modifications in the neuron and experiments are proposed that will determine the functional significance of posttranslational modifications to kinesin heavy and light chains. The applicant proposes that they may affect kinesin interactions with specific classes of membrane bounded organelles and be important for regulation of kinesin function. Factors and functional domains which form the molecular basis for interactions of kinesin with defined neuronal organelles will be defined in vitro and in vivo. The applicant proposes that kinesins are targeted to specific classes of membrane bounded organelles by unique biochemical motifs. Experiments proposed in this application are an extension of current studies by the applicant on the molecular mechanisms of fast axonal transport.